PROJECT SUMMARY ? Project 7 Use of metformin, a medicine with a 40-year track record of safety and efficacy for the treatment of diabetes and other non-malignant conditions, has been associated with improved cancer survival in observational studies. Our groups at the University of Chicago (U of C) and the Mayo Clinic (Mayo) have independently shown that ovarian cancer (OvCa) patients with diabetes who are treated with metformin have an improved prognosis. Our preclinical studies, using OvCa cell lines and mouse models, showed that metformin induces metabolic alterations in OvCa cells, inhibits interactions between cancer cells and stromal cells in the tumor microenvironment, and slows growth of both genetically engineered and xenograft models of OvCa in vivo. In view of these findings, the primary hypothesis underlying this application is that metformin can be used as a cancer therapeutic in patients with OvCa. In Aim 1, we will evaluate the effect of metformin on cells in the tumor microenvironment and on functional aspects of metabolism (glycolysis, glycogen storage, lipid homeostasis, insulin signaling). In Aim 2, we will use patient-derived xenograft models (Avatars) to evaluate the effect of metformin alone and in combination with chemotherapy on tumor burden. To assess the impact of diabetes on the action of metformin in OvCa, this experiment will be performed in both normoglycemic and obese/hyperglycemic mice. To better understand the metformin mechanism of action in OvCa, we will utilize proteomic profiling to identify the key oncogenic signaling pathways affected by metformin treatment in the patient-derived xenografts. In Aim 3, we will examine pharmacodynamic readouts and explore possible predictive biomarkers of metformin's effect with chemotherapy using biospecimens from our ongoing randomized phase II trial of chemotherapy metformin. As part of the SPORE, prospectively collected serum and tissue samples, including paired samples collected before and after neo-adjuvant chemotherapy metformin, will be used to study the effect of metformin on protein expression using shotgun proteomics followed by label-free quantification. The goal of Aim 3 is to (a) identify proteins and pathways that are altered with metformin treatment to guide research aimed at understanding the mechanism of metformin action in patients and (b) assess whether a proteomic signature in the tumor at the time of diagnosis predicts a beneficial effect of metformin treatment. Collectively, these studies will not only elucidate the mechanistic basis for metformin's effects on cancer metabolism and the microenvironment, but also provide the first prospective assessment of whether adding metformin to chemotherapy improves progression-free survival in OvCa patients.